The present invention relates generally to a printer device employing a scanning printing head, but particularly, although not exclusively, to a method of increasing the throughput of an inkjet printer device and the corresponding apparatus.
Inkjet printer devices generally incorporate one or more inkjet cartridges, often called xe2x80x9cpensxe2x80x9d, which shoot drops of ink onto a page or sheet of print media. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, Hewlett-Packard Company. The pens are usually mounted on a carriage, which is arranged to scan across a scan axis relative to a sheet of print media as the pens print a series of individual drops of ink on the print media forming a band or xe2x80x9cswathxe2x80x9d of an image, such as a picture, chart or text.
Inkjet printers are generally arranged to print in a variety of print modes that offer differing trade-offs between print quality and throughput. In high throughput modes, the print media may be advanced relative to the carriage by a distance equal to the height of a swath once a given swath is printed. In this manner, a further swath may then be printed adjacent to the earlier swath. By a repetition of this process, a complete printed page may be produced in an incremental manner.
Over recent years, the importance placed on the throughput of ink jet printers has risen dramatically. Throughput is generally measured as the number of pages of a given size, or the area of print media that a printer may ink in a given time. Consequently, manufacturers of inkjet devices have embarked on a process of continually improving their inkjet printers to give improved throughput in order to secure a competitive edge in the marketplace.
Throughput is directly related to the speed at which each swath may be printed. Therefore, in order to enable higher throughputs, inkjet devices have been developed to print at higher carriage speeds, thus allowing more swaths to be printed in a given time. However, as the carriage speed increases above a certain point, the print quality tends to deteriorate. In many cases, it is therefore preferable to print images of higher quality at a lower throughput than lower quality images at a higher throughput. Consequently, inkjet printers are being continually redeveloped to use printheads having increasingly large swath heights. By using printheads with larger swath heights, fewer swaths are needed to print a given print job. Thus, throughput may be increased.
However, even with the advent of printheads with a swath height of approximately an inch, and the prospect of printheads with significantly greater swath heights being available in the future, the demand for yet further increases in throughput remains. This is particularly true as inkjet technology is now being used or considered for use in fields traditionally dominated by other technologies.
It would therefore be desirable to provide an improved inkjet device and a method of operating an inkjet printer that addresses the problems of the prior art.
According to the present invention there is provided a method of printing an image with an inkjet printer system, said system comprising a printhead arranged to print swaths of image content parallel to a first axis on a print medium, said swaths having a width in a second axis substantially perpendicular to said first axis, said method comprising the steps of: determining the length of said image in said second axis; and, resizing said image such that said resized length of said image in said second axis is substantially an integer multiple of said swath width.
It frequently arises that the length in the direction perpendicular to the scan axis of an image to be printed is a non-integer multiple of the swath height of the printheads. This is often the case irrespective of the how wide (i.e. the distance across the image in the direction perpendicular to its length) the image is. This generally means that only a fraction of the swath height of the printheads remains to be printed in the last pass of the printheads over the print medium. The inventors of the present invention realised that in such cases, it is possible to significantly increase the speed with which an image or page could be printed by rescaling the image so as to avoid printing a final partial swath.
In a preferred embodiment of the invention, the image is rescaled, or resized, such that the length of the rescaled image is an integer multiple of the swath height of the printheads of the printer. Preferably, the size of the image is reduced such that the reduced image length is equal to the largest integer multiple of the swath height which may be divided into the original image length. That is to say that the difference between the original image length and the reduced image length is equal to the swath height of the partial swath that would normally be printed if the image were not rescaled.
In this manner, the number of swaths required to print the image is reduced by one. Thus, the time taken to print the image may be correspondingly reduced. Generally, the time taken to print a partial swath is the same as the time taken to print a swath of full height. Therefore, if an image may be printed in few swaths, the degree to which the throughput may be increased in this manner may be very significant. Thus, in general, the invention is well suited to printers having a large swath height, and furthermore to printers having a swath height that is large in relation to the length of an image to be printed in the direction of the swath height.
The throughput advantages of the present invention are particularly beneficial in devices required to print many images, or copies of an image, rapidly. For example, wherein the inkjet device is being used in the role of the printing engine of a photocopier, or a workgroup printer.
The present invention also extends to the apparatus corresponding to the method. Furthermore, the present invention also extends to a computer program, arranged to implement the method of the present invention.